Torque wrench



F. w. LIVERMoN-T 2,371,901

TORQUE WRENQH Mrch zo, 19455 y Filed Dec. l2, 1942- 181216 Z955 37 Z J6 25 56 24 ff '30 JI Patented Mar. 20, 1945 UNITED STATE-s PAT ENT OFFICE Tonarm WRENCH Frank W. Livermont,'Los Angeles, Calif., assigner of twenty per cent to W. L. Hume, thirty perl cent to Richard A Livingstoln fifteen per cent to Richard L. Ames, and five per cent to Melvin F. Vaughan, all of Los Angeles, Calif.

`Application December 12, 1942, Serial No. 468,793

("Cl. r81-53) 12 Claims.

The present invention relates particularly to torque measuring wrenches of thesnap action ty-pe which produce a distinctive.` signal. and momentarily release whena predeterminedtorque is applied.

An objectionable feature of prior `known wrenches of this type isthat they employed cam mechanisms having sliding bearing lsurfaces of such a nature that the torque necessary to trip the wrench varied greatly with a change in the friction at the' bearing surfaces. The friction could vary as a result of insuicient lubrication, excessive lubrication, accumulations of dirt, and wear, so that frequent calibration was essential.

Wrenches in accordance with the. present invention differ essentially from lprior wrenches' of the snap action type in that the snap action is obtained by means of a spring element that reverses its shape when stressed beyond a predetermined point. The use of such a spring element makes it possible to substantially eliminate sliding friction from the wrench mechanism and thereby eliminate 4the inaccuracies inherent in wrenches having substantial sliding' friction.

Several diiferent types of reversible spring elements may be employed in accordance with the invention, some examples ofwhich will now be described with reference to the drawing, in which:

Fig. 1 is a longitudinal sectional view showing what I now regard as my, preferred construction of wrench;

Fig. 2 is a section taken along the line II'-II of Figure 1, showing the shape of the spring element employed;

Fig. 3 is a View similar to Figure l but showing the wrench in a different position of operation;

Fig. 4 is a view similar to Figure 1 but showing a modied construction;

Fig. 5 is a cross. section taken `in the plane V-V of Figure 4;

Fig.' s is a View similar to Figure 1 but show- ;ing still another modification of the invention;

Figs.'.7 and 8` are cross sections taken in the planes VII-VIIv and VIII-VITI, respectively, of

Figure 6; e f

Fig. 9 is a detail section showing a of the'structure' of Fig. 1; and n Fig. l0 is a section in the plane X-X of Fig. 9. Referring first to Fig. 1, the wrench therein disclosed comprises a head Il) adapted to engage the nut or other object to be turned, which head modification projects from one end of a'hollow handle II'in which Iit is pivotally mounted. Thus the inner portion of the head I0, which is positioned within the end of the handle II, is apertured to receive a pivot sleeve I 2,l which pivot -`sleeve also extends into and s supported by apertures in the opposite side walls of the handle Il. Thehead I0 has limited'rotation in a counterclockwise direction with respect to the handle II but is held against clockwise rotation. Thus, an arm I3 on the head Ill extends into the handle and has an outer face I4'which normally lies againstone edge walll I5 of the handle to prevent ,clockwise rotation of the head III. However, other portions of the head within the handle are rounded as indicated atI6 and I'I to permit limited countervclockwise rotation of the head without interference, While at the same time maintaining more or less of a seal between the 'head and the edge v walls I5 and I8 of the handle.

v"Counterclockwise rotation of the head with respent to the mandi@ is yiemably resisted by a stiff barspring lllwhich is anchored at one end in an anchor-'block 20 mounted in the rear end of the .er and greater extent asy it is bent away from edgewall .I5 of thewrench toward the edge the, wall I8.

I` provide'an indication of the torque applied from the handle Il to thehead I0 by a mechanismfwhich responds toa predetermined deflection of the bar spring I9. Thismechanism includes a. strip spring member 23, `lying approximately alongside the bar spring I9, and a pin 2t attached to a leaf spring 25 which is secured by arivet 26 to the edge wall I8 of the handle.

The strip spring 23 hasA its opposite ends 55 notched as shown lin Fig. 2, and these notched ends are engaged by a notched supporting member 29 on the free end of the bar spring I9 and a locked in desired position of adjustment by av lock screw 33.

The free end of the leaf spring 25 normally bears against one face of the strip spring 23 adjacent the right end ofthe latter as shown in Fig. 1. The strip spring A23 is also normally engaged by a fulcrum 34 on the bar spring and is adapted to be engaged by an adjustable fulcrum screw 35, mounted in the edge wall 18, during operation of the Wrench. This operationv will be apparent from an inspection of Fig. 3, which shows the handle Il deflected clockwise with respect vto the `wrench hcad- I `just suicient to apply a torque barely less than that for which the wrench is adjusted. It will be observedthat the strip spring 23 has been carried into engagement with the end of the fulcrum screw 35 and strongly deflected between the support 29 andthe fulcrum 34 so that the upper side of the strip spring is concave between the support 28 and the fulcrumll, convex for a short distance to the right of fulcrum 34 and then concave from that point on to the rightend `of the strip. At

the :same time, the strip is compressed longi also indicated in dotted lines in Fig. 3. The pin 24 and window 36 are so located longitudinally of the handle that theyA are covered by a nger .of the workman using the wrench softhat the workman is apprized of the snapping of the strip spring by the impingement of the pin 24 against his finger. The snapping of thespring ,is .also

attended by a readily audible click so that an audible indication is also provided. Normally the fulcrum 34 engages the outwardly flexed side n of the snap spring 23.

AS soon as the force applied to the handle is released, the bar spring i9 and the head ire- .turn to. normal position and the strip spring 23 snaps back into its normal position shown in Fig. l. Although the restraining .forcey resisting clockwise rotation of the handle Il relative to the head Yl0 supplied chiefly vby ythe relatively stili bar spring |79, the. strip spring 23 supplies appreciable resistance during the nal movement of the handle relative to the head, this resistance increasing rapidly as the strip spring moves into the solid line position shownin Fig. 3 but suddenly decreasing asthe l, springY snaps over-,into the dotted line position. The reduction 4in. the

v resistance to turning rmovement afforded by the snapping over of the strip spring is sullicientto be felt bythe workman andin ordinary practice it prevents the application of torque to the nut being tightened in excess' of thatlfor which the wrench is adjusted. This is an important advantage as it permits rapid operation without danger of excessively tightening the nuts.

The wrench described can be adjusted to trip at different applied torques by varying the positions of the fulcrum screw 35 and the pin 30. In/general, retraction (upwardm'ovement) of the fulcrum screw 35 increases the torque at which the strip spring snaps over because it permits .the bar spring I9 to be deflected farther before the strip spring 23 is engaged with the fulcrum screw 35. Furthermore it is ordinarily necessary to retract the pin 3l) as the fulcrum screw 35 is retracted because as the bar spring' I9 is deflected upwardly it carries the supporting block 29 toward the pin 3B, thereby longitudinally compressing the strip spring 23 to a greater and greater extent.. vWhen the wrench is adjusted to snap at a relatively light torque, the strip spring 23 may be slightly compressed 4between the block 29 and the pin 30 when the vwrench is in normal condition as shown in Fig. l. -On .the other hand, if the fulcrum :screw 35 is retracted 'a substantial distance to adjust the wrench for the application of a relatively heavy torque, the pin 30 may have t-o be retracted so far that the strip spring .23' is not longitudinally compressed ,at all when the wrench is in the normal position shown ln Fig. l. However, the notched ends of the block 4.'Sand the pin 30 and .thenotched ends of the strip spring maintain the latter in engagement with the block 29 and the pin 30 at all times.

In all positions of adjustment, the leaf spring 25 bears against the upper face of `the strip spring 2 3, `thereby biasing it to bow downwardly as shown in Fig. l.

The fulcrum screw 3,5 .maybe of the headless type and a lock nut 31 may beprovided to hold it in a position of adjustment. It is also preferable to reinforce the edge wall I8 oi the handle with a strip 38 adjacentthe fulcrum screw 35. The 4anchor block 213 is inserted longitudinally into the handle H during assembly and retained in position by screws 39.

There is shown in Fig. 4 a simpler construction of wrench. In this instance the handle lla, Wrench head lila, anchor block 29a, and bar spring Isa correspond to the elements in Fig. 1 'but' the strip spring 23a, instead of being oatingly supported at both ends, is rigidly secured at its left end to the bar spring i911 by a screw 40. The opposite or right end of the strip spring 23a is square cut and engages in slots 4I in the block 20a on opposite sides of the end of the pin 30a. However, the longitudinal compression of the strip spring is adjusted as before by varying 'the position of the pin 36a. TheA construction shown in Fig. 4 functions the same as the structure-shown in Fig. l, as illustrated in Fig. 3. ,'I'hus, when-the bar spring 19a has lbeen deiiected sufliciently, the pressure of the fulcrum screw 35a against thefstrip 23a at a point to the left ofthe .fulcrum 34a, causes the curvature of the right end of thestrlpto reverse and'carry the pin 24a through the window 36a. It will-be'noted that 'the pin 24a is mounted directly on the strip spring 23a instead of on a separate leaf spring as in Fig. 1.

In the third modification Iof the invention, shown in Fig. 6, the strip spring 23h is similar to that in Fig. 4 except that it is dished as indicated atj42 at .its pointof contactwith the adjustable fulcrum screw 35h. It is well known that a dished disc has .a very pronounced snap vaction and this feature is utilized in the-model shown inv Fig.. 6 to accentuate 'the 'movementfof the right' end of the .strip carrying theindicating.

pin'f24b. In the construction of yFig: 6,1 it is 4not K necessary to compress the strip spring 23h longiv thevwrench by varying thecoupling between the head IU, Illa or Mib, and the bar springrlii,` 19a or'|9b,and a suitable constructionfwhereby this caribe effected is shown in Fig. 6. bThus, the underside of the left end portion of :thebar I9b isfprovided with a longitudinal groovef43 andthe arm |311 ofthe Ahead is extendedfandlikewise provided .with Va longitudinal groove 44 having upperV edges 45which engage a ball 46 .interposed between the arm |317 and the bar spring 19h. The ball46 is secured to the endof asmall. rod 4l which extends rearwardlythrough the handle alongside the 'bar` ib and through a hole 48' provided therefor in the blockZb. The free end of the rod 41 is threaded and screwed into a knurled nut 49 mounted, in av notch or slot 5bprovided in the block 26D. It. Will .be observed that by rotating the nut 49, the ball 46 can be moved longitudinally to vary the effective length of the arm 13b. Thus, when the ball.4 6 is'positioned near the kleft end of` the bar I9b, `asvsho,wn inr Fig. 6, arelatively slighttorque betweenthe head and the handle is sufcientgto produce aflarge deflection of the bar spring 9b.- Onthe other hand, if the ball 46 is moved to the right near the end of the arm 13b, a relatively largetorque must beapplied between the handleand the wrench-head to, produce the .same deflection of the bar i912. Y s,

It will be observed that the groove 44 in the arri-1 li372 `becomes progressively deeper toward the end ofthe bar. This is Ato prevent interference between the arm |31) and the rod 4l. when the arm rotates upwardly.

As best shown in Fig. `'7, aspringclick pawl 52-.may be providedto retain the nut 49 in a p0- sitionof adjustmentbut the nut v.may be turned againstthe resistance -of the pawl 52 by inserting the end of a tool, such as a screwdriver, through awindow 54 provided 'in thehandleland prying the nut in one direction or theother. ,In Fig. 1 the strip support 2 9 is nonadjustable and all adjustments of the longitudinal compression ofA the strip. are made by the screws` 32 yand 33. However, an adjustable support can` be substituted for the support 29, as shown in Figs.` 9 and 10. y l

Thus, a rivet 60, having a head 6I containing an eccentric groove B2 is tightly tted in an aperture provided therefor in the end of the bar spring IS, so that friction retains it in any position into which it maybe turned. The end of the bar spring may beslottedas indicated at 63 to permit a spring grip on the rivet 60. The end ofthe spring strip 23 is arcuate and ts into the eccentric groove 62 as shown in Fig. 10. By rotating the rivet, a very ne adjustment of the longitudinal compression of the spring can be had. To facilitate adjustingrotation, the head 6l may be provided with a polygonal socket into which a wrench may be inserted through a winthe spring strip 23.` Thu`s,1a 'l inch ywrench has been adjusted to tripat` any desiredtorque from about 65"inch poundsfto about 165 inch pounds by lvarying-tl'iebompression of the springstrip `23,' without adjustment of the screw 35. yBy also adjusting the screw 35, the range was from about `to about-1250l inch pounds. f .Although for the purpose of explaining the invention' certain specific embodiments thereof have been' described in ldetail, it is to be' understood that other `variations 'and modifications will readily occur to thoseskilled in the art and the inventionl is to belimited only to the extent `set forth in the-appendedclaims. rciaimr f* f I memberfa handle memberg'meahs rockably interconnecting said two members, spring means interposed between" s'aidtwovmembers for yieldably?I resisting rocking movement therebetween,

, said spring means lincluding a snap action element yieldable suddenly `v in response rto vdistortion beyond vva 'predetermined point and'coinprising: a stripv of spring material, a `pair of strip supporting 'ele-mentsfadapted to .bear against opposite ends offsaid stripa1 pair of'fs'trip-distorting elements -fo'r contacting said strip on opposite sides thereof,V one ofi-said elements insuring curving of said-strip in' one"`directio'n` when lsaid members are'rjinnormal position, 'and means responsive to said rocking'movement'betweensaid members for applying the other of 'said lelements against said strip withfsuiiicient force to reverse the curvature of `at least a portion thereof,`said reversal being resisted-by "longitudinal compression of said strip'between said strip4 supporting elements.

`f2. A wrenchas'describedin claim l, in which l said spring'meansfalso'comprises a spring bar for dow 64 in the wall |8.` Considerable range ofv merely varying the longitudinal compression of resistingrelative rocking motion between said two members] with one 'f said strip supporting elernents'iixedA with respect t one end of said bar, and the other 'strip supporting element xed with respect to theother end of said bar, one of said strip supporting elements being closer to said barthan the other whereby said elements are moved `tov'vard eac'zlrothenv in response lto deflection ofjsaid bar, to longitudinallycompress said A torque4 wrench .comprising an elongated hollow handle, vaworls engaging member pivotally mounted within" one end of said handle and Projecting from thev handle,s'aid work engaging member having g an. arm withiny said handle, an anchor'blockrigidly secured .in the other end of said handle, a spring bar anchored at one end in said vbloclrj-and extending through said handle into engagementwithfsaid arm for yieldably re-v deection of said bar for moving said nger into said outer position.

4. A wrench as describedl in claim 3, including adjustable means intercoupling said bar and said finger supporting means for varying the deiiection of said bar required to project said nger.

5. A wrench as described in claim 3, including a strip spring extending longitudinally within said handle, means supportingone` endrof said-)strip from the free end of saidzbar. for `lateral movement therewith, stop means` anchored to said handle for engagement with the side of said-strip adjacent said one end for deflecting said strip in response to deflection ofi said. bar, means on said block engaging the other end of said strip and functioning with said rstmentioned strip supporting means to compress -the strip longitudinally andthereby b0.wit,` fulcrum-l means on said bar engageable with the side of said strip between said stop means and Said other end, of said strip, said fulcrum means contacting the side of said strip which is outwardly ilexed and; functioning together with said stop means to reverse the curvature of said stripbetween said fulcrum and said other end in response to a predetermined deection of said bar. y 4 6. A'wrench as described inv claim 3, including a strip spring extending longitudinally AWithin said handle, first means supporting one end of said strip from the freeA end of said bar for lateral movement therewith, stopmeans anchored to said handle for engagement with one face of said strip adjacentv said one` end for delecting said strip in response to deection of said bar, second means supporting the other end of said strip from said handleand functioning with said rst strip supporting means to compressthe strip longitudinally and thereby bow it, fulcrum means on said bar engageablewith the other face, of said strip between said s topmeans-k and said other end of said strip,.said fulcrum means contacting the outwardly flexed side`of said strip and functioning together with said stop means to reverse the curvature of said strip between said fulcrum and said other end inresponse to a predetermined deection of said bar, saidl stop means and second supporting means being adjustable to vary the degree of deection, of said bar required to reverse the curvature of` said strip. e 7.. A torque Wrench comprising an elongated hollow handle, a Workl engagingk member pivotally mounted within one end of said handle and projecting from that end of` the handle,.said workV engaging member having an arm lprojecting substantially longitudinally within said handle, a bar spring within said handle and-rigidly secured to the other end thereof,` saidbar springhaving its free end adjacent and normally substantially parallel to said arm, a coupling member interposed between said arm and said bar spring and movable longitudinally therebetween fordeflecting said bar in response to rotationof said work engaging member in one direction, means for elfecting longitudinal adjustment of said coupling member, and means 'responsive' tol predetermineddeection of said bar for producing a signal. -4 i -8. A wrench as described in claim, 7, in which said means. for adjusting the longitudinal position of said coupling member comprises a flexible rod connected to said couplingmember at one end and extending longitudinally therefrom through said handle, means for laterally supporting the free end of said rod from said handle, and means for adjustably supporting said rod longitudinally in any one of a plurality of longitudinal positions.

.9. A Wrench as described in claim l in which one of said strip-supporting elements comprises an anchor member having a gripping aperture therein, a pin frictionally engaged in said aperture and projecting therefrom, the projecting portion having an annular groove therein eccentric with respect to the axis of the pin for receiving one end of said spring. Y

10. In a torque Wrench, the combination of a work-engaging member, a handle member, means rockably connecting said members, a spring means resisting rocking movement between said members, a normally curved snap spring, and means operably associated with said normally curved snap spring for reversing the curvature of the snap spring when a force is applied to the handle member of suilicient magnitude to rock the same relative to the work member.

ll.'In a torque Wrench, the combination of a work-engaging member, a handle member, means for rockably connecting said members, a spring for yieldably resisting rocking movement therebetween, said spring being mounted at one end between the handle member and having its other end engaged by ashoulder on the' Work-engagingmember, an auxiliary member mounted withinA the handle, an indicating pin operatively associated with the auxiliary member, and means operatively connectedwith the auxiliary member, spring and the handle whereby the auxiliary member is actuated when the spring is exed beyond a predetermined limit to thereby thrust the indicatingpin through a hole in the handle.

1 2. In a torque wrench, the combination of a work-engaging member, a handle member, means rockably connecting the said members, a bar spring having one end anchored within the handle member and having its other end engaged with a shoulder formed on the work-engaging member, a snap spring mounted Within the handleand connected between the handle and the bar spring whereby when the bar spring is exed beyond a predetermined limit, the snap spring is snapped.

FRANK W. LIVERMONT. 

